Comfort is a relative term that is different for virtually every individual because of sex, age, ethnicity, and activity level. Comfort is tied not only to the temperature but also to the relative humidity of an environment. Scientists have also found that a humidity level between 30 and 50 percent discourages many types of mold, dust mites, allergens, and certain bacteria. High humidity levels can cause condensation inside homes and human environmental discomfort.
Air conditioning and heating systems have been designed to remove humidity from the air. Many of these depended on reheating the cooled air either by use of additional heat from the oil or gas furnace or electric heat, both of which are cost prohibitive. Other approaches have included multiple evaporators and condensers but these were often difficult to control and required complex controls both for the temperature and the storage of refrigerant. A more common method of removing humidity with a separate dehumidifier which is independent of the air conditioner or heat pump.
There have also been attempts to reduce humidity by extending the cooling cycle after the thermostat has reached the preset cooling temperature. This is normally in conjunction with a reduction in the fan speed of the air handler motor. The reduction in fan air volume reduces the heating effect of the air passing over the evaporator which in turn lowers the temperature of the evaporator. The temperature reduction will be lowered to below the dew point temperature of the air and moisture from the air will condense on the coil thus reducing the humidity level of the interior enclosure. The current designs typically allow the temperature to be reduced below the set point of the thermostat by a preset amount thus cooling the space below that was desired. When the final temperature is reached, the unit will shut off and will not restart until cooling is called for. If the temperature inside the interior enclosure stays below the set point of the thermostat cooling is not called for and the humidity level can rise above the comfort level. This is the “clammy” or damp feeling often encountered in the Spring and Fall of the year.
Requirements by the United States Government have dictated that the efficiency of air conditioning equipment and heat pumps must meet or exceed a Seasonal Energy Efficiency Rating (SEER) of 13. Many of the manufacturers of air conditioning equipment have achieved this goal by increasing the size of both the evaporator and the condenser coils. This lowers the pressure differential across the compressor which results in less power consumption per BTU (British Thermal Unit). The increased size of the evaporator has reduced the ability of the air conditioning system to remove moisture from the air resulting in higher humidity levels. There are no federal energy saving or preserving requirements for dehumidifiers.
Phase change materials (“PCMs”) have been made to provide enhanced thermal control by inhibiting flow of thermal energy until a latent heat of the PCMs is absorbed or released during a heating or a cooling process. The PCMs can be any substance or mixture of substances that has the capability of absorbing or releasing thermal energy by means of a phase change within a temperature change. A PCMs undergoes a transition between two states, e.g., liquid and solid states, liquid and gaseous states, solid and gaseous states, or two solid states. The PCMs can effectively be recharged by a source of heat or cold. PCMs are grouped into two categories: “Organic Compounds” including but not limited to propylene and ethylene glycoils, and “salt-based Products” including but not limited to Glauber's salt. PCMs available from Entropy Solutions, Inc of Minneapolis, Minn. have very high latent heat storage capabilities per unit volume. They are capable of storing and releasing a large amount of energy as they transition between states. The peak melt temperatures of these PCMs is between −35° F. to 304° F. The PCMs are contained as microcapsules, macrocapsules, flexible films, pipes, panels, and plastic spheres. Examples of phase change materials are disclosed by Simon A. H. Rose et al in United States Patent Application Publication 2009/0227451. G. J. Suppes in U.S. Pat. No. 6,574,971 disclose a method for producing PCMs containing fatty acids or fatty acid derivatives produced by biomass or livestock such as cattle. The thermal storage ability of these PCMs can be used to eliminate the need for air conditioning and to shift an air conditioning load to non-peak demand times. In use, air is directed from inside of a building to the PCM with a fan when the temperature of the air in the building is above the temperature at which the PCM undergoes a process through which it absorbs a significant latent heat thereby cooling the air flowing back to the building.